Periodic paralysis is a rare condition that is usually inherited. It causes occasional episodes of severe muscle weakness. The two most common types of periodic paralysis are hypokalemic and hyperkalemic.
Periodic paralysis is a congenital condition, meaning it is present from birth. Familial periodic paralysis is inherited, but may occur without a known family history. Periodic paralysis is caused by abnormalities of the electrolyte channels on muscles.
The inherited form of the disorder is autosomal dominant, which means that only one affected parent is needed to transmit the gene to the baby. When one parent is affected, the child has a 50% chance of getting the disease. Rarely, the condition occurs as a result of a noninherited genetic defect.
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Factors that increase your chance of developing periodic paralysis include:
Although muscle strength returns to normal between attacks, repeated bouts of weakness may lead to chronic muscle weakness later in life. The person remains alert and aware during attacks. There is no accompanying loss of sensation.
Episodic bouts of severe weakness in the arms and legs are the most prominent symptom. Typically, these bouts occur during sleep, early morning, or after strenuous activity. Cold, stress, and alcohol may also produce attacks. Other, less common, symptoms may include:
Some features are specific to the type of periodic paralysis.
Persons with some types of periodic paralysis are at risk for a condition known as malignant hyperthermia. This can occur during the use of general anesthesia . Anyone with a family history of periodic paralysis needs to notify the anesthesiologist of this history prior to any surgery.
Because this primarily is an inherited condition, the most important aspect of diagnosis is obtaining a family history. Your doctor will ask about symptoms and your medical history. A physical exam will be done.
Attacks do not usually occur during an office visit. Your doctor may prescribe several blood tests to check potassium levels during an attack.
Your doctor may want to bring on an attack during an office visit. This should only be done under careful monitoring by an experienced neurologist. If an attack is triggered, several tests may be done, including:
If the diagnosis is in question, your doctor may do a muscle biopsy .
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Since there is no cure for periodic paralysis, lifelong treatment is usually required. Treatment focuses on preventing attacks and relieving symptoms.
There are a few behaviors you can adopt to reduce the frequency and severity of attacks:
Familial periodic paralysis cannot be prevented. Because it can be inherited, genetic counseling may be advised for couples at risk of passing on the disorder.
For the hypokalemic type, attacks may be reduced by:
For the hyperkalemic type, attacks may be reduced by:
Muscular Dystrophy Association
National Organization for Rare Disorders (NORD)
Muscular Dystrophy Canada
Hyperkalemic periodic paralysis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed . Updated March 19, 2012. Accessed October 11, 2012.
Jurkat-Ratt K, Lehmann-Horn F. Paroxysmal muscle weakness-the periodic paralyses. J Neurol . 2006;253:1391-1398.
Jurkatt-Rott K, Lerche H, Weber Y, Lehmann-Horn F. Hereditary channelopathies in neurology. Adv Exp Med Biol . 2010;686:305-334.
Miller TM. Correlating phenotype and genotype in the periodic paralyses. Neurology . 2004;63:1647-1655
Periodic paralyses. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/periodic_paralysis/periodic_paralysis.htm . Updated March 12, 2012. Accessed October 11, 2012.
Patient page: attacks of immobility caused by diet or exercise? The mystery of periodic paralyses. Neurology . 2004;63:E17-E18.
Ropper AH, Brown RH. Adams and Victor's Principles of Neurology. 8th ed. New York, NY: McGraw-Hill Medical Publishing Division; 2005: chap 54.
Last reviewed September 2012 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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